/*
 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
 *
 */

package java.security;

import java.io.*;
import java.security.cert.Certificate;
import java.security.cert.CertPath;
import java.security.cert.X509Extension;
import java.util.Date;
import java.util.List;

/**
 * This class encapsulates information about a signed timestamp.
 * It is immutable.
 * It includes the timestamp's date and time as well as information about the
 * Timestamping Authority (TSA) which generated and signed the timestamp.
 *
 * @author Vincent Ryan
 * @since 1.5
 */

public final class Timestamp implements Serializable {

  private static final long serialVersionUID = -5502683707821851294L;

  /**
   * The timestamp's date and time
   *
   * @serial
   */
  private Date timestamp;

  /**
   * The TSA's certificate path.
   *
   * @serial
   */
  private CertPath signerCertPath;

  /*
   * Hash code for this timestamp.
   */
  private transient int myhash = -1;

  /**
   * Constructs a Timestamp.
   *
   * @param timestamp is the timestamp's date and time. It must not be null.
   * @param signerCertPath is the TSA's certificate path. It must not be null.
   * @throws NullPointerException if timestamp or signerCertPath is null.
   */
  public Timestamp(Date timestamp, CertPath signerCertPath) {
    if (timestamp == null || signerCertPath == null) {
      throw new NullPointerException();
    }
    this.timestamp = new Date(timestamp.getTime()); // clone
    this.signerCertPath = signerCertPath;
  }

  /**
   * Returns the date and time when the timestamp was generated.
   *
   * @return The timestamp's date and time.
   */
  public Date getTimestamp() {
    return new Date(timestamp.getTime()); // clone
  }

  /**
   * Returns the certificate path for the Timestamping Authority.
   *
   * @return The TSA's certificate path.
   */
  public CertPath getSignerCertPath() {
    return signerCertPath;
  }

  /**
   * Returns the hash code value for this timestamp.
   * The hash code is generated using the date and time of the timestamp
   * and the TSA's certificate path.
   *
   * @return a hash code value for this timestamp.
   */
  public int hashCode() {
    if (myhash == -1) {
      myhash = timestamp.hashCode() + signerCertPath.hashCode();
    }
    return myhash;
  }

  /**
   * Tests for equality between the specified object and this
   * timestamp. Two timestamps are considered equal if the date and time of
   * their timestamp's and their signer's certificate paths are equal.
   *
   * @param obj the object to test for equality with this timestamp.
   * @return true if the timestamp are considered equal, false otherwise.
   */
  public boolean equals(Object obj) {
    if (obj == null || (!(obj instanceof Timestamp))) {
      return false;
    }
    Timestamp that = (Timestamp) obj;

    if (this == that) {
      return true;
    }
    return (timestamp.equals(that.getTimestamp()) &&
        signerCertPath.equals(that.getSignerCertPath()));
  }

  /**
   * Returns a string describing this timestamp.
   *
   * @return A string comprising the date and time of the timestamp and its signer's certificate.
   */
  public String toString() {
    StringBuffer sb = new StringBuffer();
    sb.append("(");
    sb.append("timestamp: " + timestamp);
    List<? extends Certificate> certs = signerCertPath.getCertificates();
    if (!certs.isEmpty()) {
      sb.append("TSA: " + certs.get(0));
    } else {
      sb.append("TSA: <empty>");
    }
    sb.append(")");
    return sb.toString();
  }

  // Explicitly reset hash code value to -1
  private void readObject(ObjectInputStream ois)
      throws IOException, ClassNotFoundException {
    ois.defaultReadObject();
    myhash = -1;
    timestamp = new Date(timestamp.getTime());
  }
}
